Micro-electronic package with substrate protrusion to facilitate dispense of underfill between a narrow die-to-die gap

ABSTRACT

A substrate protrusion is described. The substrate protrusion includes a top portion that extends in a first direction toward a gap between the first die and the second die and in a second direction parallel to the gap between the first die and the second die. The substrate protrusion also includes a base portion that is coupled to a substrate that extends underneath the first die and the second die. The substrate protrusion can enable void-free underfill.

TECHNICAL FIELD

Embodiments of the disclosure relate to semiconductor structures andpackaging and, more particularly to micro-electronic packages with asubstrate protrusion to facilitate the dispensing of capillary underfillmaterial between a narrow die-to-die gap.

BACKGROUND

Addressing the continuous space demands related to the integration ofelectronic packages results in smaller and smaller keep-out-zones(KOZs). A KOZ is the real estate or space on an electronic package thatepoxy material is allowed to wet. If the epoxy material wets theelectronic package outside of the KOZ, it is considered to be a KOZviolation. KOZ constraints present challenges for conventional capillaryunderfill (CUF) processes. In particular, the very small KOZs that canbe involved, can present challenges such as the insufficiency of spacefor CUF dispensing.

To address KOZ challenges, pre-applied materials, such as nonconductivepaste (NCP) and nonconductive film (NCF), have been proposed. Anadvantage provided by pre-applied materials is that no CUF dispensing isrequired. However, although such materials have been used in smallfactor packages with very low numbers of bumps, they have not been usedin medium to large die, full bump array, flip chip packages. A reasonthat they have not been used in such packages is that pre-appliedmaterials have challenges meeting chip attach yield and reliabilityrequirements. This is mainly due to the conflicting requirements forhigh chip attach yield and high chip reliability. In particular, highchip attach yield requires lower filler loading, and high chipreliability requires higher filler loading.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a cross-sectional view of a capillaryunderfill (CUF) dispensing approach for encapsulating the bottom side ofadjacent dies with a narrow die-to-die gap.

FIG. 2 is an illustration of a cross-sectional view of the CUF dispenseprocess associated with the approach of FIG. 1.

FIG. 3 is an illustration of a cross-sectional view of a package thatshows the relationship between the radius of CUF droplets that extendfrom the backside surfaces of a first and a second die, and the radiusof a CUF portion that extends from the bottom of the space between thefirst and the second die.

FIG. 4 is an illustration of a cross-sectional view of a substrate witha CUF contact protrusion to facilitate CUF contact with a substrate inaccordance with an embodiment of the present disclosure.

FIG. 5 is an illustration of cross-sectional views of example substratecontact protrusion layout schemes and substrate contact protrusiongeometries in accordance with an embodiment of the present disclosure.

FIG. 6 shows a graph of viscosity versus surface tension for variousmaterials in accordance with an embodiment of the present disclosure.

FIG. 7 is a schematic of a computer system in accordance with anembodiment of the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

A micro-electronic package with substrate protrusion to facilitatedispense of underfill between a narrow die-to-die gap. In the followingdescription, numerous specific details are set forth, such as specificmaterial and structural regimes, in order to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to one skilled in the art that embodiments of the presentdisclosure may be practiced without these specific details. In otherinstances, well-known features are not described in detail in order tonot unnecessarily obscure embodiments of the present disclosure.Furthermore, it is to be understood that the various embodiments shownin the Figures are illustrative representations and are not necessarilydrawn to scale. In some cases, various operations will be described asmultiple discrete operations, in turn, in a manner that is most helpfulin understanding the present disclosure, however, the order ofdescription should not be construed to imply that these operations arenecessarily order dependent. In particular, these operations need not beperformed in the order of presentation.

Certain terminology may also be used in the following description forthe purpose of reference only, and thus are not intended to be limiting.For example, terms such as “upper”, “lower”, “above”, and “below” referto directions in the drawings to which reference is made. Terms such as“front”, “back”, “rear”, and “side” describe the orientation and/orlocation of portions of the component within a consistent but arbitraryframe of reference which is made clear by reference to the text and theassociated drawings describing the component under discussion. Suchterminology may include the words specifically mentioned above,derivatives thereof, and words of similar import.

FIG. 1 is an illustration of a cross-sectional view 100 of the result ofa capillary underfill (CUF) dispensing approach for encapsulating thebottom side of adjacent dies with a narrow die-to-die gap (the gapdefined by the space between the adjacent dies). Shown in FIG. 1 iscapillary underfill (CUF) encapsulant material 101, first die 103,second die 105, encapsulant flow stopping point 107, die-to-die gap 109,bottom side electrical connectors 111, underfill region 113, and packagesubstrate 115. FIG. 1 illustrates a drawback of a conventional capillaryunderfill approach for encapsulating the bottom side of adjacent dieswith a narrow die-to-die gap. Referring to FIG. 1, as part of theapproach, the CUF encapsulant material 101 is dispensed into thedie-to-die gap 109 between the first die 103 and the second die 105. TheCUF encapsulant material 101 is dispensed to flow downward (vertically),within the die-to-die gap 109, between the first die 103 and the seconddie 105. Because of insufficient space for CUF dispensing andinsufficient capillary pressure, physical forces acting upon the CUFencapsulant material 101 can cause a stopping point of encapsulant flow107 to be reached before bottom side electrical connectors 111 areencapsulated. In the FIG. 1 example, the stopping point of theencapsulant flow 107 occurs near the bottom of the die-to-die gap 109.

Conventional CUF approaches such as that illustrated in FIG. 1 are notsuitable for the dispense of underfill material into narrow die-to-diegaps. The technical challenges encountered using such approaches caninclude but are not limited to: (1) stoppages of the flow of the CUFencapsulant material 101 at the die-to-die gap (instead of filling theunderfill region 113) and (2) the depositing of significant amounts ofthe CUF encapsulant material 101 onto one or both of the adjacent dieswhich can cause down-stream assembly problems.

The CUF encapsulant material 101 is dispensed in fluid form into thedie-to-die gap 109 in order to fill the space underneath the first die103 and the second die 105 such that the bottom side electricalconnectors 111 that are located in the underfill region 113 areencapsulated. In particular, the CUF encapsulant 101 encapsulates thebottom side electrical connectors 111 positioned between the bottom sidesurfaces of the first die 103 and the second die 105 and the packagesubstrate 115. The CUF encapsulant material 101 can be dispensed usingan automated/computerized dispense platform. In embodiments of thedisclosure described herein, such as with reference to FIGS. 4-6, theCUF encapsulant material 101 can be dispensed in any suitable manner ofdispensing CUF encapsulant material. The CUF encapsulant material 101can include but are not limited to epoxy materials. In embodiments ofthe disclosure described herein, such as with reference to FIGS. 4-6,the CUF encapsulant material can be any material that is suitable forencapsulating the underfill region 113. The advantages provided by theencapsulation of the underfill region can include but are not limited toprotecting the bottom side electrical connectors 111 from cracking andproviding shock resistance.

The first die 103 and the second die 105 are semiconductor dies that arepositioned side by side on the package substrate 115 and are coupled tothe package substrate 115 through bottom side electrical connectors 111.The die-to-die gap 109 that separates the first die 103 and the seconddie 105 can be very narrow. In some cases the die-to-die gap can be asnarrow as 100 um. In other cases the die-to-die gap can be narrower.Conventional CUF dispense processes are not compatible with adjacent diearrangements that include such narrow die-to-die gaps. An unsatisfactoryunderfill process can result in the underfill material stopping in thedie-to-die gap (see FIG. 1). In addition, an unsatisfactory underfillprocess can result in an “epoxy on die” condition that can negativelyimpact processing operations (see FIG. 1 at top of die).

Bottom side electrical connectors 111 couple the first die 103 and thesecond die 105 with the package substrate 115. Bottom side electricalconnectors 111 can include solder bumps and attached pads (see FIG. 1).The solder bumps can be attached to pads of the package substrate 115 ordie pads of a semiconductor die.

The package substrate 115 mounts the first die 103 and the second die105. The package substrate 115 is coupled to the first die 103 and thesecond die 105 through the bottom side electrical connectors 111. Thepackage substrate 115 is also used to electrically couple the first die103 and the second die 105 to other components or devices of anelectronic system. For example, different types of passive elementsand/or integrated circuits. The package substrate 115 can include amultilayered structure (see FIG. 1). The multilayered wiring substratestructure can use vias to provide interlayer connectivity.

FIG. 2 is an illustration of cross-sectional views of the CUF die-to-dieencapsulant dispensing and flow process associated with the approach ofFIG. 1. The packaging processes involved can include but are not limitedto flip chip or ball grid array (BGA). Typically, the encapsulation isintended to be completed free from air entrapment.

Referring to FIG. 2, at 201, CUF encapsulant droplets 201 a aredispensed toward the die-to-die gap that is located between the firstdie 103 and the second die 105. The droplets are intended to encapsulatethe electrical connectors (e.g., 111 in FIG. 1) in the underfill region113 that is located between the bottom side surfaces of the first die103 and the second die 105 and the top surface of the package substrate115.

At 202, the CUF encapsulant droplets dispensed at 201 contact the backside surfaces of the first die 103 and the second die 105 and remain fora period of a few milliseconds. Referring to FIG. 2, the dispenseddroplets cover the opening of the die-to-die gap between the first die103 and the second die 105.

At 203, the CUF encapsulant flows in two competing directions,horizontally on the back side surfaces of the first die 103 and thesecond die 105, and vertically in the gap between the first die 103 andthe second die 105. The horizontal and vertical flows occursimultaneously. Based on these flows two scenarios can result. Thescenario that results depends upon properties of the encapsulantmaterial (see discussion made with reference to FIG. 6). The twoscenarios are described with reference to operations 204 a and 204 bwhich are illustrated in FIG. 2.

At 204 a, the CUF encapsulant flow into the die-to-die gap is thedominant flow direction, whereas the CUF encapsulant flow on the backside surfaces of the first die 103 and the second die 105 is minimal.This flow pattern results in a high contact angle of CUF encapsulant onthe back side surfaces of the first die 103 and the second die 105. Dueto hydrostatic pressure balance, the radius of the CUF encapsulantdroplets extending from the back side surfaces of the first die 103 andthe second die 105, and the radius of the CUF encapsulant portionextending from the bottom of the die-to-die gap between the first die103 and the second die 105, are directly related in terms of theirrelative magnitudes which are labelled R1 and R2 in FIG. 3. For example,a large R1, extending from the back side surfaces of the first die 103and the second die 105, can cause a large R2, extending from the bottomof the die-to-die gap between the first die 103 and the second die 105,to be generated. Consequently, based on the large R1, the hydrostaticpressure balance at 204 a is sufficient to cause the CUF encapsulant tocontact the package substrate 115. When the CUF encapsulant makescontact with the package substrate 115, the capillary force drives theCUF encapsulant flow into the underfill region 113, as shown in 205 a.

At 204 b, in contrast to the flow pattern described at 204 a, the CUFencapsulant flow on the back side surfaces of the first die 103 and thesecond die 105 is the dominant flow direction. Moreover, the CUFencapsulant flow in the die-to-die gap between the first die 103 and thesecond die 105 is correspondingly slow. This causes a low contact angleof the CUF encapsulant on the back side of surfaces of the first die 103and the second die 105. As a result, R1 and R2 are both small and theCUF encapsulant cannot reach the package substrate 115. Consequently,there is insufficient capillary force to drive the CUF encapsulant flowinto the underfill region 113 such that the CUF encapsulant stops at thedie-to-die gap.

FIG. 4 is an illustration of a cross-sectional view of a substrate witha CUF contact protrusion to facilitate CUF encapsulant contact with thesubstrate according to an embodiment. It should be appreciated that CUFencapsulant contact with the substrate is important to encapsulating theunderfill region of adjacent dies with a narrow die-to-die gap. In anembodiment, the CUF contact protrusions facilitate CUF encapsulantcontact with the substrate in order to effect a successful underfill. Inan embodiment, the CUF contact protrusions can be speed bump likestructures that are formed on the substrate (either organic substrate orSi wafer) to facilitate the contact of the CUF encapsulant with thepackage substrate. FIG. 4 shows CUF encapsulant 401, first die 403,second die 405, CUF contact protrusion 407 and package substrate 409. InFIG. 4, at 400 the CUF encapsulant 401 makes contact with the CUFcontact protrusion 407. It should be appreciated that contact is madewith the CUF contact protrusion 407 although in the example of FIG. 4,the CUF flow on the back side surfaces of the first die 403 and thesecond die 405 is the dominant flow direction. Moreover, the CUFencapsulant flow in the die-to-die gap between the first die 403 and thesecond die 405 is correspondingly slow, which as discussed above, causesa low contact angle of the CUF encapsulant on the back side surfaces ofthe first die 403 and the second die 405. However, even though R1 and R2are both small, and the CUF encapsulant 401 does not reach the mainsubstrate surface 411, contact is made with the CUF contact protrusion407. The contact that the CUF encapsulant 401 makes with the CUF contactprotrusion 407 generates a capillary force that drives the CUFencapsulant flow into the underfill region 413 such that the underfillregion 413 is filled. In this manner, the bottom sides of the first die403 and the second die 405 are encapsulated and the underfill process issuccessfully completed. FIG. 4 illustrates that in an embodiment, usingCUF contact protrusions 407, the CUF encapsulant can more readily makecontact with the package substrate 409. Facilitating this contactenables the successful encapsulation of the underfill region 413 offirst and second adjacently positioned dies that have a narrowdie-to-die gap.

In an embodiment, the CUF dispense of encapsulant between adjacent dieswith a die-to-die gap as narrow as 100 um is enabled. Additionally,embodiments enable CUF dispense between adjacent dies on complicatedmultichip packages, with minimal need for materials development andadditional equipment requirements.

FIG. 5 is an illustration of cross-sectional views of example substratecontact protrusion layout schemes and substrate contact protrusiongeometries according to an embodiment. In FIG. 5, example substratecontact protrusion layout schemes are shown at 500 and example substratecontact protrusion geometries are shown at 550. Referring to FIG. 5, at500, example contact protrusion layout schemes include first die 501 andsecond die 505 and contact protrusion layout patterns 503, 509 and 515.The contact protrusion layout pattern 503 has a monolithic structurethat lies underneath, and extends parallel to the space between thefirst die 501 and the second die 505. The contact protrusion layoutpattern 509 includes a plurality of individual protrusions that lieunderneath, and extend parallel to the space between the first die 501and the second die 505. The individual protrusions of contact protrusionlayout pattern 509 have a rectangular top view cross sectional profile.The contact protrusion layout pattern 515 includes a plurality ofindividual protrusions that lie underneath, and extend parallel to, thespace between the first die 501 and the second die 505. The individualprotrusions of the contact protrusion layout pattern 515 have a circularcross sectional top view profile. Referring again to FIG. 5, at 550, theexample substrate contact protrusion geometries include front viewcross-sectional profiles that are rectangular 551, stacked (rectangular)553, hemispheric 555 and trapezoidal 557. It should be appreciated thatthe substrate contact protrusion layout schemes and substrate contactprotrusion geometries described with reference to FIG. 5 are exemplaryand that any other suitable substrate contact protrusion layout schemesand substrate contact protrusion geometries can be used in accordancewith embodiments of the present disclosure.

In an embodiment, the length of a protrusion can be determined by theCUF dispense length and the die size. For example, in an embodiment, theminimum length of the protrusion can be determined to be similar to theCUF dispense length and the maximum length of the protrusion can bedetermined to be the same or slightly larger than the die size. In anembodiment, the height of the substrate contact protrusions can be lowerthan the chip gap height, and the width of the substrate contactprotrusions can allow a minimum distance of approximately 20 um from theSi die corner/sidewall for the flow of CUF encapsulant. In otherembodiments the substrate contact protrusions can have other heights andcan have other widths.

In an embodiment, the position of a substrate contact protrusion can beon the substrate and aligned to the middle of the die-to-die gap. Inother embodiments, the position of a substrate contact protrusion can beto the left or the right of the middle of the die-to-die gap. In anembodiment, a substrate contact protrusion can be positioned anywherethat is suitable for facilitating CUF encapsulant contact with thesubstrate.

In an embodiment, the material makeup of a substrate contact protrusioncan be the same as the substrate material or can be a combination of thesubstrate material and another material or materials. In an embodiment,the material makeup of the substrate contact protrusion can include butis not limited to solder resist or buildup layer in the case of anorganic substrate, and silicon, silicon oxide, silicon nitride and/ormetals in the case of a silicon substrate. In other embodiments, stillother materials that are suitable for forming a substrate contactprotrusion can be used to form a protrusion.

FIG. 6 shows a graph of viscosity versus surface tension for variousmaterials and the impact of viscosity and surface tension on flowcharacteristics in the die-to-die dispense process. FIG. 6 showsviscosity versus surface tension for CUF materials CUF A 601, CUF B 603and CUF C 605. In an embodiment, of the materials CUF A 601, CUF B 603and CUF C 605, CUF A 601 has the lowest viscosity and the intermediatesurface tension, CUF B 603 has the intermediate viscosity and thehighest surface tension and CUF C 605 has the highest viscosity and thelowest surface tension. In an embodiment, improvements to die-to-diedispense process margin can be made by maintaining CUF viscosity andsurface tension in a range such that a suitable contact angle isachieved. FIG. 6 shows that surface tension and viscosity are modulatorsfor contact angle and consequently the flow between die-to-die gaps. Inan embodiment, CUF should have high surface energy (greater than 34mN/m) and fast flow into die-to-die gaps (approximately 0.8 Pa·sviscosity) to achieve a high contact angle. In other embodiments, CUFcan have other surface energies and flow characteristics to achieve ahigh contact angle. It should be appreciated that lower surface energyon the Si die backside can lead to a higher CUF contact angle. Inaddition, in an embodiment, hydrophobic coating on the Si die backsidecan be used to accelerate the die-to-die flow.

FIG. 7 is a schematic of a computer system 700, in accordance with anembodiment of the present disclosure. The computer system 700 (alsoreferred to as the electronic system 700) as depicted can embody asemiconductor package that includes a substrate protrusion for causingunderfill material to fill space underneath a first die and a seconddie, according to any of the several disclosed embodiments and theirequivalents as set forth in this disclosure. The computer system 700 maybe a mobile device such as a netbook computer. The computer system 700may be a mobile device such as a wireless smart phone. The computersystem 700 may be a desktop computer. The computer system 700 may be ahand-held reader. The computer system 700 may be a server system. Thecomputer system 700 may be a supercomputer or high-performance computingsystem.

In an embodiment, the electronic system 700 is a computer system thatincludes a system bus 720 to electrically couple the various componentsof the electronic system 700. The system bus 720 is a single bus or anycombination of busses according to various embodiments. The electronicsystem 700 includes a voltage source 730 that provides power to theintegrated circuit 710. In some embodiments, the voltage source 730supplies current to the integrated circuit 710 through the system bus720.

The integrated circuit 710 is electrically coupled to the system bus 720and includes any circuit, or combination of circuits according to anembodiment. In an embodiment, the integrated circuit 710 includes aprocessor 712 that can be of any type. As used herein, the processor 712may mean any type of circuit such as, but not limited to, amicroprocessor, a microcontroller, a graphics processor, a digitalsignal processor, or another processor. In an embodiment, the processor712 includes, or is coupled with, a package that includes a substrateprotrusion for causing underfill material to fill space underneath afirst die and a second die, as disclosed herein. In an embodiment, SRAMembodiments are found in memory caches of the processor. Other types ofcircuits that can be included in the integrated circuit 710 are a customcircuit or an application-specific integrated circuit (ASIC), such as acommunications circuit 714 for use in wireless devices such as cellulartelephones, smart phones, pagers, portable computers, two-way radios,and similar electronic systems, or a communications circuit for servers.In an embodiment, the integrated circuit 710 includes on-die memory 716such as static random-access memory (SRAM). In an embodiment, theintegrated circuit 710 includes embedded on-die memory 716 such asembedded dynamic random-access memory (eDRAM).

In an embodiment, the integrated circuit 710 is complemented with asubsequent integrated circuit 711. Useful embodiments include a dualprocessor 713 and a dual communications circuit 715 and dual on-diememory 717 such as SRAM. In an embodiment, the dual integrated circuit710 includes embedded on-die memory 717 such as eDRAM.

In an embodiment, the electronic system 700 also includes an externalmemory 740 that in turn may include one or more memory elements suitableto the particular application, such as a main memory 742 in the form ofRAM, one or more hard drives 744, and/or one or more drives that handleremovable media 746, such as diskettes, compact disks (CDs), digitalvariable disks (DVDs), flash memory drives, and other removable mediaknown in the art. The external memory 740 may also be embedded memory748 such as the first die in a die stack, according to an embodiment.

In an embodiment, the electronic system 700 also includes a displaydevice 750, an audio output 760. In an embodiment, the electronic system700 includes an input device such as a controller 770 that may be akeyboard, mouse, trackball, game controller, microphone,voice-recognition device, or any other input device that inputsinformation into the electronic system 700. In an embodiment, an inputdevice 770 is a camera. In an embodiment, an input device 770 is adigital sound recorder. In an embodiment, an input device 770 is acamera and a digital sound recorder.

As shown herein, the integrated circuit 710 can be implemented in anumber of different embodiments, including a package substrate having asubstrate protrusion for causing underfill material to fill spaceunderneath a first die and a second die, according to any of the severaldisclosed embodiments and their equivalents, an electronic system, acomputer system, one or more methods of fabricating an integratedcircuit, and one or more methods of fabricating an electronic assemblythat includes a package substrate having a substrate protrusion forcausing underfill material to fill space underneath a first die and asecond die, according to any of the several disclosed embodiments as setforth herein in the various embodiments and their art-recognizedequivalents. The elements, materials, geometries, dimensions, andsequence of operations can all be varied to suit particular I/O couplingrequirements including array contact count, array contact configurationfor a microelectronic die embedded in a processor mounting substrateaccording to any of the several disclosed package substrates having asubstrate protrusion for causing underfill material to fill spaceunderneath a first die and a second die embodiments and theirequivalents. A foundation substrate may be included, as represented bythe dashed line of FIG. 7. Passive devices may also be included, as isalso depicted in FIG. 7.

Although specific embodiments have been described above, theseembodiments are not intended to limit the scope of the presentdisclosure, even where only a single embodiment is described withrespect to a particular feature. Examples of features provided in thedisclosure are intended to be illustrative rather than restrictiveunless stated otherwise. The above description is intended to cover suchalternatives, modifications, and equivalents as would be apparent to aperson skilled in the art having the benefit of the present disclosure.

The scope of the present disclosure includes any feature or combinationof features disclosed herein (either explicitly or implicitly), or anygeneralization thereof, whether or not it mitigates any or all of theproblems addressed herein. Accordingly, new claims may be formulatedduring prosecution of the present application (or an applicationclaiming priority thereto) to any such combination of features. Inparticular, with reference to the appended claims, features fromdependent claims may be combined with those of the independent claimsand features from respective independent claims may be combined in anyappropriate manner and not merely in the specific combinationsenumerated in the appended claims.

The following examples pertain to further embodiments. The variousfeatures of the different embodiments may be variously combined withsome features included and others excluded to suit a variety ofdifferent applications.

The following examples pertain to further embodiments. The variousfeatures of the different embodiments may be variously combined withsome features included and others excluded to suit a variety ofdifferent applications.

Example embodiment 1: A substrate protrusion comprises a top portionextending in a first direction toward a gap between a first die and asecond die and in a second direction parallel to the gap between thefirst die and the second die. A base portion is coupled to a substratethat extends underneath the first die and the second die.

Example embodiment 2: The substrate protrusion of embodiment 1 whereinthe substrate protrusion is located between the first die and the seconddie.

Example embodiment 3: The substrate protrusion of embodiment 1 wherein aback side of the first die and the second die is coated with hydrophobicmaterial.

Example embodiment 4: The substrate protrusion of embodiment 1 whereinthe substrate protrusion is monolithic.

Example embodiment 5: The substrate protrusion of embodiment 1, 2, 3 or4 wherein the substrate protrusion comprises a plurality of discreteparts.

Example embodiment 6: The substrate protrusion of embodiment 1 whereinthe substrate protrusion has a rectangular shape.

Example embodiment 7: The substrate protrusion of embodiment 1 whereinthe substrate protrusion has a hemispheric top surface.

Example embodiment 8: The substrate protrusion of embodiment 1, 2, 3, 4,5, 6, or 7 wherein the substrate protrusion has a trapezoidal shape.

Example embodiment 9: A substrate comprising a protrusion extending in afirst direction toward a gap between a first die and a second die and ina second direction parallel to the gap between the first die and thesecond die. The substrate includes a first portion coupled to theprotrusion and extending beneath the first die and a second portioncoupled to the protrusion and extending beneath the second die.

Example embodiment 10: The substrate of embodiment 9 wherein theprotrusion extends from a top surface of the substrate.

Example embodiment 11: The substrate of embodiment 9 wherein theprotrusion is located between the first die and the second die.

Example embodiment 12: The substrate of embodiment 9, 10, or 11 whereina back side of the first die and the second die is coated withhydrophobic material.

Example embodiment 13: The substrate of embodiment 9 wherein theprotrusion is monolithic.

Example embodiment 14: The substrate of embodiment 9 wherein theprotrusion comprises a plurality of discrete parts.

Example embodiment 15: The substrate of embodiment 9 wherein theprotrusion has a rectangular shape.

Example embodiment 16: The substrate of embodiment 9, 10, 11, 12, 13,14, or 15 wherein the protrusion has a hemispheric top surface.

Example embodiment 17: The substrate of embodiment 9, 10, 11, 12, 13,14, or 15 wherein the protrusion has a trapezoidal shape.

Example embodiment 18: A method of providing underfill between a narrowdie-to-die gap, comprising dispensing underfill material toward a gapbetween adjacent dies. The method includes causing the underfillmaterial to contact a protrusion that extends from a substrate towardthe gap. The underfill material is caused to fill the space underneaththe adjacent dies based on the contact with the protrusion.

Example embodiment 19: The method of embodiment 18 wherein the causingthe underfill material to contact a protrusion that extends from asubstrate toward the gap comprises causing the underfill material tocontact a protrusion that is located between the die-to-die gap.

Example embodiment 20: The method of embodiment 18 or 19 furthercomprising forming a hydrophobic coating on a backside of the adjacentdies.

What is claimed is:
 1. A package, comprising: a substrate comprising aprotrusion; a first die coupled to the substrate; a second die coupledto the substrate, the protrusion extending in a first direction toward agap between the first die and the second die and in a second directionparallel to the gap between the first die and the second die, wherein afirst portion of the substrate is coupled to the protrusion and extendsbeneath the first die, and wherein a second portion of the substrate iscoupled to the protrusion and extends beneath the second die; and anencapsulant over the protrusion of the substrate, the encapsulantextending beneath the first die, and the encapsulant extending beneaththe second die.
 2. The package of claim 1 wherein the protrusion extendsfrom a top surface of the substrate.
 3. The package of claim 1 whereinthe protrusion is located between the first die and the second die. 4.The package of claim 1 wherein a back side of each of the first die andthe second die is coated with hydrophobic material.
 5. The package ofclaim 1 wherein the protrusion is monolithic.
 6. The package of claim 1wherein the protrusion comprises a plurality of discrete parts.
 7. Thepackage of claim 1 wherein the protrusion has a rectangular shape. 8.The package of claim 1 wherein the protrusion has a hemispheric topsurface.
 9. The package of claim 1 wherein the protrusion has atrapezoidal shape.
 10. A method, comprising: dispensing underfillmaterial toward a gap between adjacent dies; causing the underfillmaterial to contact a protrusion that extends from a substrate towardthe gap; and causing the underfill material to fill space underneath theadjacent dies based on the contact with the protrusion.
 11. The methodof claim 10 wherein the causing the underfill material to contact theprotrusion comprises causing the underfill material to contact theprotrusion between a die-to-die gap.
 12. The method of claim 10 furthercomprising forming a hydrophobic coating on a backside of the adjacentdies.